1. Field of the Invention
The present invention relates generally to an optical fiber payout system, and, more particularly, to such a system for paying out a fiber from an airborne missile dispenser to form a data link with launch site equipment.
2. Description of the Related Art
Many present day weapon systems include a missile having a filament data link that is maintained with launch site apparatus throughout a part or all of the missile flight. Specifically a length of metal wire or an optical fiber is wound into a stack aboard the missile and, in the usual situation, the other end of the fiber is anchored at the launch site. On launch, the dispenser allows the filament to unwind at a sufficiently rapid rate in order to maintain the link.
A number of criteria must be met achieving a satisfactory filament dispensing system for serving as a missile data link. Initially, payout has to be accomplished with a minimum of tension on the filament to prevent breakage and, in the case of an optical fiber, it is even necessary to prevent micro-bending which has been found can substantially reduce the quality of signal transmission. Because of this problem, placement of the dispenser on the missile has to be carefully considered and ducting or guiding of the filament during dispensing can only be accomplished in a manner not tending to stress or bend the optical fiber.
Also, where the missile is being hot launched, difficulty is presented in that either the fiber must be dispensed in a manner to avoid the hot propulsion gases, or steps must be taken to prevent the fiber from being injured or destroyed by contact with the hot gases. Still further, it is necessary to prevent a condition termed "pre-dispensing" which, in essence, is the initial increase in the dispensing rate due to the rapid flow of propulsion gases resulting in excess filament being dispensed during the early stages of missile flight.
It is desirable to be able to pass the filament through the propulsion gases on dispensing in order to avoid the mentioned difficulties of bending, breaking or stressing the filament that frequently occurs when the fiber is directed along an out of the way path in order to avoid passing through the propulsion gases.